Seed-borne and early season diseases and pests pose devastating consequences to crop production if not adequately managed, as germinating seeds and emerging plants are particularly vulnerable to damage during early growth stages. Therefore, it is of utmost importance to provide appropriate protection to seeds and emerging plants from seed- and soil-borne pests and diseases. Traditionally, this has been achieved by applying pesticides directly into the soil, mostly under the form of granules. In an effort to reduce the impact of pesticides on public health and on environment, more recent advances in pest control include the application of pesticides directly onto the seeds under the form of compositions for seed treatment. A broad spectrum of technologies is being practiced nowadays to treat seeds in order to provide seed and plant protection and to improve the establishment of healthy crops. These methods for seed treatment include dressing, coating and pelleting of the seeds.
It remains technically challenging to prepare suitable compositions for seed treatment as such compositions should satisfy a whole range of requirements: the composition should adhere well to the surface of the seed to avoid easy wash-off of the active substance and to reduce dust formation during sowing, but should at the same time not result in making the seeds sticky, such that the seeds would adhere to each other and form conglomerates, or such that seed storage or handling could be hampered by seeds sticking to the wall of the storage container or by seeds clogging sowing equipment or by reduced flowability of the seeds through a seed planter, resulting in uneven seed planting. Moreover, the composition should not reduce the storage life or life span of treated seeds, the composition should not adversely affect the germination of the seeds, e.g., by impairing water and gas exchange from the environment to the seed once planted and the composition should not cause damage to the seed or the seedling due to the phytotoxicity of the active substances present in the composition for seed treatment.
In order to ensure accessibility of the seed upon germination, U.S. Pat. No. 2,651,883, U.S. Pat. No. 3,707,807 and U.S. Pat. No. 3,598,565 describe methods for seed treatment using water-soluble polymer coatings, so that the coating would dissolve to allow exposure of the seeds to the environment for development. U.S. Pat. No. 3,316,676 and U.S. Pat. No. 4,245,432 relate to water-insoluble but water-sensitive seed coatings, the integrity of which is destroyed or which disintegrate when in contact with water. Although these methods allow for a good contact between the seed and its environment during germination, the rapid dissolution or disintegration of the seed coating will also cause a quick loss of the active substances contained in the seed coating. U.S. Pat. No. 5,876,739 describes a non-phytotoxic polymer-based film coating for seeds, which allows controlled release of an insecticide over a prolonged period of time. WO 2007/103076 and WO 2010/107312 also describe that polymer-based coating of seeds can be lubricated to facilitate flowability during planting. However, the coating is still based on aspecific sticking of the polymer to the seed, and plant-enhancing agents should be incorporated in a surplus of coating material.
There is still a need for a composition for seed treatment that allows a specific binding of the plant-enhancing agent to the plant seed, resulting in a thin and permeable coating, without unwanted loss of the plant-enhancing agent in the environment.